In this study, a 3D motion capture method is proposed for a flexible object with point features. Firstly, the method utilizes two calibrated high-speed cameras to capture motion video of a flexible object, and makes a stereo rectification of the image. Secondly, through the Difference Of Gaussian (DOG) algorithm, the positions of the feature points are obtained, and the extreme of feature points is extracted. Thirdly, matching pairs in a certain range of windows are searched, the feature points of the left and right images are matched. Thirdly, 3D reconstruction is realized by triangulation. Finally, using the search strategy to match the time series, the 3D motion capture of a dynamic flexible object is realized, and the spatial coordinates, velocity, and acceleration parameters are calculated. The experimental results show that the method is more accurate than the method of using SIFT algorithm to match the feature points to capture the flexible moving object.